Definition
Creep corrosion is a failure mode in which a corrosion product, most commonly copper sulfide, forms on exposed metal and then creeps across an otherwise non-corroding surface such as solder mask or a noble-metal finish. As the conductive sulfide spreads, it can bridge the gap between adjacent pads or traces and create leakage paths or shorts. Unlike dendrite growth, creep corrosion does not require a voltage bias; it is driven chemically by sulfur and moisture.
Conditions that trigger it
The key ingredients are a sulfur-bearing atmosphere (hydrogen sulfide and related gases found near certain industrial sites, paper mills, agricultural operations, or some heating systems) combined with elevated humidity. Immersion-silver (ImAg) surface finishes are notably susceptible, with copper sulfide as the dominant product and a smaller fraction of silver sulfide. ENIG and OSP finishes are generally more resistant. Failures in harsh environments can appear within months of deployment.
Implications for miners
Mining hardware is sometimes sited in barns, near generators, or in unfiltered industrial air where sulfur compounds are present, exactly the conditions that accelerate creep corrosion. Defenses include choosing more resistant surface finishes, applying a protective conformal coating, filtering intake air, and controlling humidity. Discolored, dark, or powdery deposits creeping outward from pads are a warning sign worth investigating before they bridge conductors.
For the bias-driven cousin of this mechanism, see our entry on dendrite growth.
In Simple Terms
Creep corrosion is a failure mode in which a corrosion product, most commonly copper sulfide, forms on exposed metal and then creeps across an otherwise…